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Discussion Starter #1 (Edited)
Hi All,

I live in the UK and recently bought a 1993 Kawasaki VN750 with the mileage showing 10,000 miles (not sure how true this is...).
I took the bike home and started carrying out some checks. 1st thing was the engine oil was below the 'low' mark on the window and the coolant has brownish colour to it. I'm presuming the bike has overheated? I've topped the oil up but left the coolant as it is for now until I establish if the bike will start. After that I will remove the system and flush through.

Also, for some reason the starter relay and all of the spark plugs were missing, so I purchased a new relay, fitted it, charged the battery and the starter/ engine seems to turn ok (without plugs in it). I presume this would mean the engine isn't seized.

I am picking up some new plugs tonight. Before I install them and try to properly start the bike, is there any other checks I should do as I do not want to cause any further damage (if there is any).

Thanks in advance,
 

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Hi Pete just top the oil up then if you get it running I would change the oil and filter and new coolent Halford pink anti freeze which does not have silicates in it then take it from there. I am in the uk and just finished my vn rebuild
 

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If you Google kawasaki original parts which is cradleys in birmingham you can get a parts list for the vn up which gives you all the prices from memory cam chains about £20 each head gaskets £13 but you can't get a full gasket set you have to buy them separately if you have to rebuild make a list has you take it apart
 

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Having no spark plugs worries me. I wonder what all may have gotten into the cylinders through the spark plug holes. You need to clean out the tank and put fresh gas in it. I don't know what is available in the UK, but I use Maxima Coolanol coolant. It is specifically made for motorcycles. Whatever you do, DON'T USE DEXKILL. It will destroy your engine. DEXKILL is a mechanics term for a GM product they call Dexcool. It goes in as a red or orange liquid, and then turns into a brown waxy gooey mess inside the engine, plugging up the entire cooling system. The carburetors may also be plugged up from sitting with gas in them. If you have ethanol gas there, the problem may be much worse. Removing and reinstalling the carbs for cleaning is not a fun job, but at least it is free. No expensive parts involved.

As far as rebuilding a Vulcan 750 engine, it has been done, but I wouldn't do it, and I am an auto mechanic with 37 years experience. There is a series of videos on here somewhere about a guy that actually did it. If it needs many new parts, you could buy a brand new motorcycle for less than the price of the parts. I never did figure out how the Japanese could build a $5000 motorcycle out of $25,000 worth of parts and include the labor free.
 

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I am not a auto mechanic and I have rebuilt 2 vn750 engines it's not rocket science if you want or need help or advice feel free to pm me your mobile no. were abouts in the uk are you?
 

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I am in the U.S. I work on bikes, but the only motorcycle engines I have ever actually rebuilt have been 2 stroke dirt bike engines. I have built and rebuilt a lot of car engines, including high dollar drag race engines. Mostly small block Chevys. I have also built a few air cooled VW engines. The Vulcan engine is a lot more complex than either one of those. I had to give up my job as a mechanic after 37 years (with the same employer) due to disabilities. I still work on cars and bikes, it just takes longer and is a lot more painful. I no longer work on any electronic or computer parts. Mechanical only. I have no interest in electronics (on vehicles, I am an amateur radio operator, but even there I prefer tube radios) and no longer have tools and diagnostic equipment to do that kind of thing anyway. Four of my five cars and all 6 of my bikes are carbureted. One of my cars is a street legal drag racer, and makes almost 600hp. I built the engine myself except for the machine work. I see working on the Vulcan as being more like working on a clock rather than a car or simpler motorcycle. It has twice as many parts as your average v-twin motorcycle. I blew an engine in my '02 Vulcan 750 (broken cam chain) and never even considered trying to repair it. I recently bought a nice low mileage 1997 model, and will be getting it road ready this summer (here in Phoenix, AZ, where it reaches 118+ degrees F) winter is riding season.

The Vulcan 750 engine, in typical Japanese fashion, was never intended to be rebuilt. Unlike car engines, when worn cranks and cams can be reground, cylinders rebored, valve seats replaced, and undersized bearings and oversized pistons and rings installed, large expensive parts have to be replaced. If a Vulcan crank or con rod bearing fails, you have the replace the whole pressed together assembly. You have no way to even check con rod bearing clearances. Cams run directly in the head, with no bearings. So excessive wear means replacing the cams and heads, rather than just the bearings. It can get real expensive real quick. As far as I know, the last truly rebuildable motorcycle engine was the Harley EVO.
 

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My apologies Jerry my comment was not aimed at you or your ability but to help a vn owner in the uk and your view that you can't rebuild a vn750 engine is wrong has you can still get big ends mains rings ect yes they are more complex than a evo engine is true but they can and have been rebuilt I my self have done 2
 

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It's okay, you gave Jerry his needed excuse to copy paste his massive experience that his inexplicably led to a complete inability to work on many things.
 

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Discussion Starter #10
Hi All,

I have done a bit more investigation.

Im only getting spark from the front 2 plugs, so I'm presuming I need a new coil for the rear 2 plugs - is a coil easy to change over? Am I right in thinking that the engine should still start with only 2 out of the 4 plugs sparking (albeit the engine will run rubbish). At this point I'm just trying to establish if the engine starts/ runs.

When I press the start button it turns over very slowly for about 2 seconds then nothing happens (it sounds like it is struggling to turn over). Im getting about 12.6/12.7V from my battery with the ignition turned off. When I turn the ignition on and press the start button the V drop to about 9.8/9.9. I hooked up a car battery up to my bike battery via jump leads but this didn't really change anything.

On thing that doesn't make sense to me is that I've stripped the carbs and cleaned with carb cleaner and compressed air, yet the spark plugs don't seem to be 'wet' from petrol? Why wouldn't the plugs be getting fuel even after I've cleaned them? They were really clean and the pilot and main jet wasn't blocked. The float wasn't gummed up either and is at the correct angle.

Anymore help and advice would be much appreciated :)

Where about in the UK are you Trev?

Thanks,

Pete
 

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Discussion Starter #11
Also when I turn the key the only light that comes on is the neutral light (green). Is this correct? I thought the red oil light should also come on?
 

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Is there petrol in the carbs loosen the screw on bottom of float bowl see if petrol comes out is the vacuum pipe connected
It could run on one cylinder but it would take some cranking to get it going the rear coil is bolted to the battery carrier a bit fiddly to change but easy
I have sent you a pm with my mobile if you need to chat look in your message's
I live in Leeds Yorkshire
 

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Discussion Starter #13
Is there petrol in the carbs loosen the screw on bottom of float bowl see if petrol comes out is the vacuum pipe connected
It could run on one cylinder but it would take some cranking to get it going the rear coil is bolted to the battery carrier a bit fiddly to change but easy
I have sent you a pm with my mobile if you need to chat look in your message's
I live in Leeds Yorkshire
Hi,

I've checked the float bowls and both are getting fuel. The amount of hoses on the carbs confuses me a bit, I have 4 in total, 2 are fuel hoses and I think the other 2 are vent hoses. One of the vent hoses was connected to the fuel petcock and the other hose has a bolt in the end of it?? Im trying to start the bike using a auxiliary fuel tank and I've connected the 2 fuel hoses together with a 'Y' piece connector.

I have just read your PM, I really appreciate the offer.

Thanks,

Pete
 

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Each carb has its own inlet the two inner ones that are connected together are the overflow the petrol tap has two outlets one to each carb then on the left carb there is a a short pipe that connects to the petrol tap and on the right carb if that one is blanked of that one is to to do with the US emissions law which you don't really need
I would make sure the engine is turning freely first take a plug out from each cylinder take the little left cover off held on with three crosshead screws and then use a 17mm socket and see if you can turn it anti clockwise freely DO NOT TURN IT Clockwise sorry forgot to say you need to drop the oil to take cover off
 

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Discussion Starter #15
Each carb has its own inlet the two inner ones that are connected together are the overflow the petrol tap has two outlets one to each carb then on the left carb there is a a short pipe that connects to the petrol tap and on the right carb if that one is blanked of that one is to to do with the US emissions law which you don't really need
I would make sure the engine is turning freely first take a plug out from each cylinder take the little left cover off held on with three crosshead screws and then use a 17mm socket and see if you can turn it anti clockwise freely DO NOT TURN IT Clockwise sorry forgot to say you need to drop the oil to take cover off

Hi,

Tonight I drained the oil and took out each spark plugs individually and manually turned the engine anticlockwise. The good news is I was able to turn the engine. The engine was hard to turn, then a bit easier to turn, then hard to turn ... etc etc. Im presuming this is normal and relates to the pistons moving up and down?

Not sure what the next step should be? Ive ordered another coil to get the rear 2 spark plugs sparking, from there I guess I will need to buy a new battery? I read somewhere the vn750 needs at show atleast 10V when the start button is pushed - is this correct? I get just under 10v at the moment.

Also, im now getting fuel showing on the spark plugs :smiley_th

Thanks,

Pete
 

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It's okay, you gave Jerry his needed excuse to copy paste his massive experience that his inexplicably led to a complete inability to work on many things.
Just because you can work on some things doesn't mean you can work on everything. I really have no doubts I could disassemble and reassemble a VN750 engine. But like I said, there are a lot of things in it that can't be checked, like in a car engine, and a lot of parts that if they are found to be worn beyond spec, would cost a fortune to replace. If anybody plans to rebuild a VN750 engine, I suggest watching ALL of Andrew Roth's videos (he was known as Roach on here. Don't know what ever happened to him. I located his videos on YouTube.

https://www.youtube.com/results?search_query=roth+vn750+videos.

He never checked the crank or con rod bearings in those videos, he just assumed (or maybe hoped would be a better term) that they were ok. Simply taking an engine apart and putting it back together is not rebuilding it. EVERY single thing must be checked and either found to be within tolerances or replaced, and the design of the Vulcan 750 engine makes that extremely cost prohibitive (which is the case with all Japanese motorcycle engines, it's just that the VN750 has about twice as many parts as the average Japanese v-twin. Way back in 1969, the first CB750 was the first motorcycle engine that was cheaper to replace than rebuild. Before that most motorcycle engines were designed to be rebuilt.

First make sure you are getting fuel to the carbs. Open the drain screw on each one and see if there is gas in the float bowls. The VN750 carbs do not have an accelerator pump, so you may not be getting enough liquid gas into the cylinders to wet the plugs if it doesn't turn over for very long.

All Vulcan 750s turn over slowly, it's just the way they are, but they should continue to turn over. And yes, you should be able to get it to fire on only one cylinder. Another quirk the Vulcan 750 has is after sitting for some time with gas left in the carbs, it will sometimes start up on the front cylinder, and it can take some time for the rear cylinder to kick in. I have no idea why it does this. But if you have spark, compression, and a close to correct air/fuel mixture, then the front cylinder should at least fire. The rear coil is not difficult to replace. A car battery, fully charged, has way more than enough power to start a Vulcan 750. It sounds like you may have some electrical issues. The oil light should also come on. I could have sworn on my 2002 the headlight did not come on until the engine started, but on my newly purchased 1997, the headlight, tail light, and all the instrument lights come on with the key in the on position. It still starts up ok.

There are 2 large hoses that go from the petcock to the carbs. These are fuel lines. The Vulcan has a vacuum operated petcock. The small hose that goes from the front carb is just to supply vacuum to the petcock. The small hose on the rear carb is part of the PAIR (emissions system) which has probably been removed, and it should be plugged up. Oh, there is one more hose that connects to the carbs. That is the float bowl vent. The two carbs share a common float bowl (somewhat unusual) and on a stock bike that vent is plugged into a hole in the right air filter housing.

With the plugs out, there will be no compression, so there should be no change in resistance when turning the engine over by hand. It should turn easily all the way around. I wonder is something is binding inside the engine, making it harder than it should be to turn over. That could overload the starter, make it turn slower, and pull more power than it is supposed to from the battery. It would also make the starter motor get really hot, and I would think it should eventually blow a fuse. The starter is not connected to the engine, so it would have nothing to do with how it feels when turning it over by hand. It sounds like, for some reason, a problem is causing your engine to be harder than normal to turn over.
 

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Discussion Starter #17
Just because you can work on some things doesn't mean you can work on everything. I really have no doubts I could disassemble and reassemble a VN750 engine. But like I said, there are a lot of things in it that can't be checked, like in a car engine, and a lot of parts that if they are found to be worn beyond spec, would cost a fortune to replace. If anybody plans to rebuild a VN750 engine, I suggest watching ALL of Andrew Roth's videos (he was known as Roach on here. Don't know what ever happened to him. I located his videos on YouTube.

https://www.youtube.com/results?search_query=roth+vn750+videos.

He never checked the crank or con rod bearings in those videos, he just assumed (or maybe hoped would be a better term) that they were ok. Simply taking an engine apart and putting it back together is not rebuilding it. EVERY single thing must be checked and either found to be within tolerances or replaced, and the design of the Vulcan 750 engine makes that extremely cost prohibitive (which is the case with all Japanese motorcycle engines, it's just that the VN750 has about twice as many parts as the average Japanese v-twin. Way back in 1969, the first CB750 was the first motorcycle engine that was cheaper to replace than rebuild. Before that most motorcycle engines were designed to be rebuilt.

First make sure you are getting fuel to the carbs. Open the drain screw on each one and see if there is gas in the float bowls. The VN750 carbs do not have an accelerator pump, so you may not be getting enough liquid gas into the cylinders to wet the plugs if it doesn't turn over for very long.

All Vulcan 750s turn over slowly, it's just the way they are, but they should continue to turn over. And yes, you should be able to get it to fire on only one cylinder. Another quirk the Vulcan 750 has is after sitting for some time with gas left in the carbs, it will sometimes start up on the front cylinder, and it can take some time for the rear cylinder to kick in. I have no idea why it does this. But if you have spark, compression, and a close to correct air/fuel mixture, then the front cylinder should at least fire. The rear coil is not difficult to replace. A car battery, fully charged, has way more than enough power to start a Vulcan 750. It sounds like you may have some electrical issues. The oil light should also come on. I could have sworn on my 2002 the headlight did not come on until the engine started, but on my newly purchased 1997, the headlight, tail light, and all the instrument lights come on with the key in the on position. It still starts up ok.

There are 2 large hoses that go from the petcock to the carbs. These are fuel lines. The Vulcan has a vacuum operated petcock. The small hose that goes from the front carb is just to supply vacuum to the petcock. The small hose on the rear carb is part of the PAIR (emissions system) which has probably been removed, and it should be plugged up. Oh, there is one more hose that connects to the carbs. That is the float bowl vent. The two carbs share a common float bowl (somewhat unusual) and on a stock bike that vent is plugged into a hole in the right air filter housing.

With the plugs out, there will be no compression, so there should be no change in resistance when turning the engine over by hand. It should turn easily all the way around. I wonder is something is binding inside the engine, making it harder than it should be to turn over. That could overload the starter, make it turn slower, and pull more power than it is supposed to from the battery. It would also make the starter motor get really hot, and I would think it should eventually blow a fuse. The starter is not connected to the engine, so it would have nothing to do with how it feels when turning it over by hand. It sounds like, for some reason, a problem is causing your engine to be harder than normal to turn over.
Thanks for all this info, it is much appreciated.

I'm definitely getting fuel to the float bowls and the plug ends are now 'wet' so that issue is resolved. The hoses that should be on the float bowl vents have been removed for some reason.

It sounds like my findings aren't as good as I'd hoped. What is the most likely cause of the binding (I still suspect the bike overheated as the coolant is a brownish colour)? Or is it a case of it could be anything? Any advice on where to look next would be much appreciated. I am by no means a mechanic but I can carry out maintenance works and have rebuild top ends on 2 stroke dirt bikes - I appreciate this engine will be a completely different kettle of fish but I'm happy to try and learn :)

Also, I will take a closer look at the oil light - hopefully its as simple as a blown bulb!

Thanks,

Pete
 

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Pete with the plugs out and in neutral you should feel very little resistance if it goes tight in places I think there is something a miss in the engine if you try and start it with a decent battery you could do more damage if you are not going to do anything with it if its goosed fine give it a go but if you are I would take the engine out and start investigating
 

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Discussion Starter #19
Pete with the plugs out and in neutral you should feel very little resistance if it goes tight in places I think there is something a miss in the engine if you try and start it with a decent battery you could do more damage if you are not going to do anything with it if its goosed fine give it a go but if you are I would take the engine out and start investigating
Hi Trev,

Just checking, I took each plug out individually (I.e I had 3 plugs in each time I manually turned it). Was I supposed to take all 4 out at the same time and then try and manually turn it?

Thanks,

Pete
 
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